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NeXtMidas Training
File Handlers
Introduction
Definitions
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- Some Definitions:
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When a primitive reads from a file, it gets a handle to the "file object." The
"file object" is realy an instance of one of the NeXtMidas File Handlers. That
file handler in turns uses an Resource Type to read the raw bytes from the file.
- File Handler
- The class responsible for interpreting a file.
- Uses an I/O Resource to read the raw bytes.
- Defined in REG.HANDLERS.FILE
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- Resource Type
- The class responsible for reading raw bytes from a file, HTTP socket, etc.
- Knows nothing about the underlying file structure.
- Defined in REG.HANDLERS.RESOURCE (Entries for SYS file handlers are
not included in this table, this may change in the future.)
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- Generally there is a separate Resource Type that corresponds to each protocol type
in a URL. For example:
file:///.../myfile.tmp -> FileResource
http:///.../myfile.tmp -> HttpResource
ram:myfile.tmp -> RamResource
xmpipe:_mypipe -> XmPipeResource
Note that while the name of a File Handler often matches the file extension
(e.g. CsvFile for .csv or DbfFile for .dbf)
this is not required. The same is also true for a Resource Type.
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